DESCRIPTION JPH04207699

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DESCRIPTION JPH04207699
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
pressure vibration detecting elements such as condenser microphones and ceramic microphones.
[Prior Art] The structure of a conventional pressure vibration detecting element will be described
by taking a condenser microphone as an example. That is, the cross-sectional structure of the
condenser microphone (+) is shown in FIGS. 4 to 6, and the explanation thereof will be made. The
condenser microphone has been widely used conventionally as one part of acoustic equipment
(for example, As Primo ICEM-EM-1211, the detailed description will be omitted and briefly
described. (2) is a case where a lead wire extraction hole (2a) is provided at the bottom, (3) is a
circuit board to which a FET (lantic resistor) 4 is attached, and the case (2) from the circuit board
(3) A lead wire (not shown) is drawn to the outside through the hole (2a) of. (5) is a cylindrical
spacer holding / supporting member having upper and lower open ends, and a plurality of ringshaped insulating spacers (7) are provided between the upper end surface (5a) and the tip bent
portion (2b) of the case (2). The peripheral portion of the electret film (.6a) forming the pressure
receiving surface and the counter electrode (6b) thereof is nipped across the whole. Therefore, as
shown in FIG. 5, in the condenser microphone (1), a minute gap (10) is formed in the vicinity of
the tip bent portion (2b) of the case (2), and the condenser microphone via the gap (10) The air
confined in the space formed in (1) flows so as to leak, and the pressure fluctuation generated
outside causes the electret film (6a) to bend and be formed between the counter electrode (6b)
The capacitance is changed, 1 pressure fluctuation is converted to a gas signal. Also, as shown in
FIG. 6, a gap (10) is generated between each of the members (2), (3) and (s) at the bottom of the
condenser microphone (1) as shown in FIG. The air of the space formed inside the condenser
microphone (1) flows through the hole (2a) of 2). In addition, one lead terminal (4a) of the abovementioned FE Th Lansistor (4) is always electrically connected to the counter electrode (6b) of
the electret film (6a). [Problems to be Solved by the Invention] However, since -a commercially
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available microphones including this type of condenser microphone and the like have been
developed for sound use, the lower frequency is only up to about 20 Hz which can be heard by
the human ear. Under the present circumstances that frequency characteristics are not
measured, and catalogs and products are not guaranteed, using microphones in the low
frequency range such as 0.1) Tz, 1l-Tz etc. is performance-wise , Also due to its structure.
Therefore, I measured the frequency characteristics of the above-mentioned condenser
microphone (+) which was not published as a catalog value (it was not measured in practice) by
using a home-made measuring device shown in FIG. As IHz -1. It is found that anti-resonance
characteristics (portion where the characteristics are in the shape of 7) occur between OHz, and
that the characteristics as a sensor for measurement in the low frequency range are not
possessed, and such frequency Based on the characteristics, it was experimentally proved that it
is impossible to detect physical phenomena such as the movement of a human having a slow
movement characteristic of about 0.1 to 10 Hz using pressure fluctuation. [Means for Solving the
Invention] So, I made a completely new improvement to be able to measure up to very low
frequencies using low-cost general-purpose audio microphones, especially condenser
microphones. A microphone, that is, a pressure vibration detection element is proposed, in which
the pressure vibration detection means is disposed so as to close the opening at one end of the
cylinder, and the cylinder is leaked from the air other than the opening Try to close the road.
[Operation] Low frequency characteristics such as 0.1 Hz and I Hz so as to extremely reduce the
flow of gas between the space formed behind the pressure receiving portion of the pressure
vibration detecting means such as the condenser microphone as described above and the outside
To improve the [First Embodiment] The configuration will be described based on FIG. 1, but the
description of the same or equivalent parts as the parts described in FIGS. 4 to 6 will be omitted,
and only different parts will be described. Give an explanation. In FIG. 1, (13) is an adhesive layer
which adheres the circuit board (3) to the inner bottom wall surface of the case (2). The circuit
board (3) and the case (2) shown in FIG. The clearance (10) formed between the inner bottom
wall and the inner wall is eliminated, and the flow of air inside and outside the case (2) through
the hole (2a) of the case (2) is prevented. However, in this case, needless to say, holes for
mounting components and the like should not be drilled in the portion of the hole (2a) position of
the case (2) of the circuit board (3). It is shown in FIG. 2 that the frequency characteristics in the
low frequency region of the condenser microphone (1) have been improved to the vicinity of 0.1
Hz after the anti-resonance has been eliminated by adopting the above configuration. 7 Second
Embodiment The structure of this embodiment will be described with reference to FIG. 3. The
same structure as or an equivalent portion to the parts described in FIGS. 1 and 5 to 6 will be
described. The explanation is omitted and only different parts are explained.
First, in FIG. 3, the difference from FIG. 1 is that the sealing agent (14) is used from the outside of
the hole (2a) of the case (2) in FIG. 3 without using the adhesive layer (13) in FIG. Sealed to
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prevent the flow of air inside and outside the case (2). That is, the sealant (14) blocks the lead
wire drawing hole (2a) of the case (2) from the outside, and prevents the flow of air inside and
outside the case (2). Thereby, the frequency characteristic similar to that of the above
embodiment is obtained as shown in FIG. In the above embodiment, an example in which the
condenser microphone is used as a pressure vibration detection element has been described.
However, it is needless to say that the invention is not limited thereto, and any similar device
having a similar function may be used. It is. As described above, according to the present
invention, in the pressure vibration detecting element in which the pressure vibration detecting
means is disposed so as to close the opening at one end of the cylinder, the cylinder is not the
opening. Since the pressure vibration detecting element is characterized in that the air leakage
path is closed, the effect that the frequency characteristic of the low frequency region can be
greatly improved easily with a simple configuration is exhibited. In particular, the conventional
condenser microphone can significantly improve the frequency characteristics in the low
frequency range without any modification, and can not be expensive and can obtain an
inexpensive element. it can.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view of an essential part of a condenser microphone according to a first
embodiment of the present invention, and FIG. 2 is a frequency characteristic diagram of those
shown in the first and second embodiments. The principal part cross-sectional explanatory
drawing of the condenser microphone of an Example, FIG. 4 is a cross-sectional explanatory
drawing of the conventional condenser microphone, 5th and 6th are for demonstrating the air
leak path of the condenser microphone shown in FIG. The principal part cross-sectional
explanatory drawing, FIG. 7 is a frequency characteristic view of the condenser microphone
shown in FIG.
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